World 1 through World 8 completed in New Super Mario Bros. DS. This walkthrough shows all of the star coins and secret exits in the game. Below are the time stamps for each particular World in the game.
00:01 to 18:35 - World 1
18:45 to 41:17 - World 2
41:20 to 1:05:50 - World 3
1:05:51 to 1:31:12 - World 4
1:31:15 to 1:58:46 - World 5
1:58:57 to 2:24:55 - World 6
2:24:58 to 2:58:18 - World 7
2:58:20 to 3:31:30 - World 8